Find out if Mesh Operator (bpy.ops.mesh...) was cancelled or not via python
This looks at the TRANSFORM_OT_translate.value Vector as shown in the 'INFO' reports.  If the operator was cancelled it returns (0, 0, 0) else has a length.

import bpy

wm = bpy.context.window_manager

print("TESTing Extrude Op")
for op in wm.operators:
    if op.bl_idname == 'MESH_OT_extrude_region_move':  #name == 'Extrude Region and Move'
        print(op.name, "Found")
        v = op.macros['TRANSFORM_OT_translate'].properties.value
        if v.length:
            print("operator used")
        else:
            print("operator canceled")